The Stovebolt Site Forums The Shop Area Engine Shop dual master

hello all. i read all the previous posts about using a '69 mustang master for a dual conversion setup, and it seems it's the best one to use. my question is, will it work on a 1 ton truck? what mods if any do i have to make? i can fab my own bracket. im not planning to haul anything, and i don't care about keeping the truck original, i just don't trust my stock master. i think it has a leak. btw, my truck is a 48 GMC. thanks!

Just a couple of points to keep in mind, oneton-first (most important) make sure that master cylinder will displace enough fluid to properly operate your wheel cylinders/calipers. Second, make sure to design/build your bracket in such a way as to allow free pedal travel (no binding) and make sure the master cylinder pistons are bottomed out before the pedal hits the floor. Oh yeah, if you are using disc brakes (maybe even if you are using drums) you may want to look into residual pressure valves in the lines, to keep wheel cylinder or caliper pistons from creeping back between stops. Best of luck, let us know how it works out.

Wannabe

P.S. Oh yeah, A proportioning valve appropriate to your particular brake setup might be a good idea too. Hope these ideas help.

I am looking at doing the same for my 55 1 ton. Keeping it in the stock location. How did the 69 master cylinder work? Did you use the proportion or the pressure valve? I will buy a bracket for mine though. Anyone have any preferences on which is best? Or to to stay away from? Thanks!

The early mustang master cyl have the porp valve built in. Thats why they are recommended.

I'm pretty sure the dual-resevoir power brake unit I ordered was manufactured by Master Power , although I can't recall which vendor took my money. It came with a bracket made of 3/8" steel which bolted to the frame using the original master's holes. The offset is required for the booster to clear the frame rail, and the unit came with an offset rod to connect to the stock pedal. My only complaint is the offset puts the resevoir just left of the transmission cover; there's enough room to tip a bottle of brake fluid but it's a bit of a pain to pull the floor (I usually check the fluid level on a creeper using my mirror on a stick). Remote resevoirs are becoming quite popular, I may look into that one day....

The only problem specific to the 1-ton is the static pressure required to fill the cylinders on the huge drum brakes. I don't have any residual valves on the front, and a proportioning valve on the rear to balance the bias under loads; it has too much pedal travel but it will lock up all 4 tires if you stab the brake. I'll be installing some residual valves soon to get the mush out of the pedal.

Be sure you jettison all the old hard line; it is not only prone to failure since brake fluid collects moisture (internal corrosion is common), but it's also routed wrong for dual-stage masters. Get some hardline and a bending tool from NAPA and start from scratch.